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Frank P. McKxbben 



[Reprinted from Technology Quarterly, Vol. XIX, No. 3, September, 190G] 



TENSION TESTS OF STEEL ANGLES WITH VARIOUS TYPES 

OF END-CONNECTION' 



By frank p. McKIBBEN 



The tension tests which form the subject of this paper were made 
in the testing laboratory of the Massachusetts Institute of Technology 



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Fig. I. — Tension Tests of 
Steel Angles 

(Nine Types of End-Connection 
Tested) 

Note. — All angles had both ends 
alike. All angles 5 ft. 4 ins. in 
length. Rivets, |-in Holes punched, 
^|-in . Pin holes, 2-in . diameter drilled. 



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[ Angle B2 

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upon twenty-seven specimens of rolled steel angles, such as are used 
for tension members in riveted structural work. They were made with 
a view of studying the following points : 

I. The ultimate strength of the angles in tension. 



1 A paper read before the American Society for Testing Materials at Atlantic City, N. J.j 
June 23, 1906. Reprinted from Engineering News, July 5, 1906, 56, No. i. 



Tension Tests of Steel Angles 



307 



2. The value of a lug in transmitting stress from the outstanding 
leg of the main angle into the hitch plate. 

3. The relative strength of angles where the gauge line for rivets 
and where the centre of gravity line, respectively, pass through the 
centre of the pull. 

4. The relative strength of single angles and angles riveted together 
to form pairs. 

There are three specimens of each of nine different types, making 
in all twenty-seven specimens. These are shown in detail in Figure i. 
Each of the main angles, 5 feet 4 inches in length, is riveted at each 
end to a hitch plate. 

Types A-^, B-^, and C^ consist each of one angle, 32X3X8 inches, 
4X3X1 inches, and 6X4X1 inches, respectively, riveted to the 
hitch plates by one leg only. 



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Fig. 2. — Tension Rigging for Tests of Steel Angles 

Types Ag, B2, and C^ consist each of one angle of the same size 
as Aj, Bj, and C^, respectively, and have both legs connected to the 
hitch plates, the outstanding leg being connected by means of a lug 
angle. 

Each specimen of types D^ and D2 is made up of two 3 X 3 X yg 
inch angles, one on either side of the hitch plate. D^ is not, and Dg is, 
provided with lugs for each of the outstanding legs of the main angles. 

In each of the types just mentioned the gauge line for rivets in the 
main angle is run through the centre line of pull. In the case of angles 
with unequal legs the long leg is placed in contact with the hitch plates. 

Type Bg consists of one 4X3X1 inch angle connected to the 
hitch plates by one leg only. It differs from type B^ in that the Hne 
of pull coincides with a projection of the centre of gravity line instead of 
with the gauge line for rivets. 



'Ti'^uie Inn^t 



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Frank P. McKibbcn 




vvithout lug. with \\ic^. 





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without lug 



3^3-^" NOS. 25,26. 



3x3""^" No. 27. 

with lu^. 



wilh lug . 

Fig. 3. — Sketches of Fractures of Steel Angles with Various 
Types of End-Connection 

(Small figures at fracture indicate origin and progress of rupture) 

The end-connections were designed to insure failure in the main 
angles, and the specimens were made as long as could be tested con- 
veniently. The hitch plate at each end of each specimen was provided 
with two 2-inch holes, by means of which it was pinned between two 
holding plates, fastened in turn by a single pin to a third plate gripped 
by the testing machine. A diagram of this holding device is shown in 
Figure 2. 

All of the pieces of angles of a given size were cut from one long 
angle, and from each of these long pieces there were made also two 
small tensile test specimens. Table I gives the average results of 
the tensile tests on the small specimens, which were approximately 
18 X li X f or Y^g inches in size. 

TABLE I — Tensile Strength of Small Test Specimens Cut from 

Steel Angles 



Size of angle from which specimen was.cut 


3^ X 3 X i inches 


4x3x1 inches 


6 X 4 X f inches 


3X3X finches 


Yield point, pounds per square inch . . . 


33,160.0 


31,600.0 


32,600.0 


34,800.0 


Ultimate strength, pounds per square inch 


59,300.0 


54,000.0 


51,600.0 


61,000.0 


Elongation, per cent, in 8 inches .... 


28.0 


28.6 


31.1 


29.5 


Reduction of area, per cent 


48.9 


54.6 


56.5 


52.6 


Appearance of fracture 


Silky 


Silky 


Silky 


Silky 





Figure 3 shows diagrammatically the outUnes of the various frac- 
tures, all of which occurred in the main angles. There was no failure 
of rivets. The numbers on the sketches show the sequence of the 



Tension Tests of Steel Angles 



309 



fractures. With the exception of one of the specimens, made of two 
3X3X^6 inch angles, failure took place at one of the inner rivets 
which connects the angle to the hitch plate — that is, the connecting 
rivet which lies nearest the centre of the specimen. In the case of 
the exception noted rupture occurred at the centre of the specimen, 
where there is a single rivet connecting the two angles together. In 
all cases, just before failure the metal between the inner rivet and the 
outer edge of the leg connected by that rivet to the hitch plate drew 
down considerably at both ends of the specimen. Failure then occurred 






Enci.News, 



Fig. 4. — Views OF Three of the Test Specimens after Fracture 
(No. 27 was the only specimen which did not break at the end-connection) 

at this point, continuing slowly across the horizontal leg and then up 
the vertical leg. With the one exception cited, failure occurred, in all 
specimens having lugs, on a zigzag section passing through rivets in 
the horizontal and in the vertical legs. In order to secure the greatest 
strength from an angle in tension this zigzag section should be equal 
to or greater than the net right section. In none of the specimens 
tested is this the case. Consequently the total ultimate strength of 
some of the specimens with lugs is less than that of similar specimens 
without the lugs. However, the strength per square inch of net area 
is greater where the lugs are provided, showing that with the proper 
spacing of rivets to utilize the maximum net area the lug is an 
advantage. 



310 



Frank P. McKibben 



Table II shows in detail the results of the tests. Table III shows 
the per cent, increase in the strength per square inch of net area due 
to the lugs. 

TABLE II — Summary of Tension Tests on Steel Angles 





C 
V 

B 


6 


.a 

u 

B 

'e 



iz; 


Cross Section. Area 
IN Square Inches. 


Breaking 
Load. 


is 

° a 
•£.3 
c > 




i 


1 
1 


(A 

8 
B 

u 

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V 

3^ . 

Mum 

^ = is 


Remarks. 














Lbs. 


Lbs. 


% 




A^ 

a; 


1 
2 
3 

Mean 


3J X 3 X 1 
3^ X 3 X 1 
3i X 3 X i 
3^ X 3 X i 


2.30 
2.30 
2.30 
2.30 


2.29 
2.32 
2.35 
2.32 


1.95 
1.98 
2.00 
1.98 


89,500 
96,100 
95,200 
93,600 


45,900 
48,500 
47,600 
47,400 


77.4 
81.8 
80.2 
79.8 


^ Without lugs 


A, 

a; 


4 

5 

6 

Mean 


3^ X 3 X i 
3^ X 3 X i 
3^ X 3 X i 
3^ X3 X i 


2.30 
2.30 
2.30 
2.30 


2.28 
2.28 
2.27 
2.28 


1.78 
1.78 
1.77 
1.78 


84,600 
88,600 
91,200 
88,100 


47,500 
49,800 
51,500 
49,600 


80.1 
84.0 
86.8 
83.6 


V With lugs 


1: 


7 

8 

9 

Mean 


4 X3 X f 
4X3 X i 
4X 3X f 
4X3X1 


2.49 
2.49 
2.49 
2.49 


2.44 
2.42 
2.50 
2.45 


2.10 
2.09 
2.15 
2.11 


85,000 
84,000 
85,600 
84,900 


40,500 
40,100 
39,800 
40,100 


75.0 
74.3 
73.7 
74.3 


> Without lugs 


B2 


10 

11 

12 

Mean 


4X3X1 
4X3X1 
4 X 3 X f 
4X 3 X i 


2.49 
2.49 
2.49 
2.49 


2.42 
2.43 
2.45 
2.43 


1.92 
1.92 
1.95 
1.93 


83,500 
85,100 
84,100 
84,200 


43,500 
44,300 
43,100 
43,600 


80.5 
82.0 
79.9 
80.8 


\ With lugs 


B3 
B3 


13 

14 

15 

Mean 


4X3X1 
4X3X1 
4X3 X f 
4X3X1 


2.49 
2.49 
2.49 
2.49 


2.41 
2.42 
2.41 
2.41 


2.07 
2.09 
2.07 
2.08 


88,600 
90,400 
91,000 
90,000 


42,800 
43,200 
44,000 
43,300 


79.3 
80.0 
81.4 
80.2 


"j Without lugs 
1 Centre of gravity line 
1 through pull 


1 


16 
17 

18 
Mean 


6X4X1 
6X4X1 
6 X4X f 
6 X 4 X i 


3.61 
3.61 
3.61 
3.61 


3.53 
3. .54 
3.50 
3.52 


3.11 
3.12 
3.07 
3.10 


131,000 
125,700 
128.200 
128,300 


42,100 
40,300 
41,800 
41,400 


81.6 
78.1 
81.1 
80.3 


> Without lugs 




19 

20 

21 

Mean 


6 X4 X 1 
6 X4 X f 
6 X 4 X f 
6 X4 X i 


3.61 
3.61 
3 61 
3.61 


3.50 
3.50 
3.50 
3. .50 


3.04 
3.03 
3.04 
3.04 


131,500 
130,200 
131,900 
131,200 


43,300 
42,900 
43,400 
43,200 


84.0 
83.2 
84.1 
83.7 


► With lugs 




22 

23 

24 

Mean 


Two3 X 3 X ^B 
Two 3 X 3 X t\ 
Two 3 X 3 X t\ 
Two3 X 3X ^s 


3.56 
3.56 
3.56 
3.56 


3.44 
3.43 
3.49 
3.45 


2.88 
2.87 
2.91 
2.89 


134,100 
136,500 
139,100 
136,600 


46,600 
47,700 
47,800 
47,400 


76.4 

78.3 

78.4 
77.7 


\- Without lugs 


D2 


25 
26 

27 
Mean 


Two 3 X 3 X /s 
Two3 X 3 X t\ 
Two3 X3 X i'b 
Two 3 X 3 X fs 


3.56 
356 
3.56 
3.56 


3.43 
3.43 
3.42 
3.43 


2.69 
2.69 
2.86 
2.75 


137,900 
140,400 
138,800 
139,000 


51,200 
52,200 
48,500 
50,600 


84.0 
85.6 
79.6 
83.1 


► With lugs 



^ Figures of previous column compared with specimen tensile test results of Table I. 



The results of the tests show that the ultimate strength per square 
inch of net section for angles having gauge lines for rivets passing 
through the centre of pull varies, for the single angles, from 39,800 
to 51,500 pounds, which is approximately from 74 per cent, to 87 per 
cent, of the strength of the tensile test specimens ; and for angles 



Tension Tests of Steel Angles 



311 




H 
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312 



Frank P. McKibben 



riveted together in pairs, from 46,600 to 52,200 pounds, which is 
approximately T7 per cent, to 86 per cent, of the strength of the 
material as developed by the tensile test specimens. 

The efficiency of the lug is shown by the fact that for specimens 
provided with lugs there is an increase over specimens not so provided 




Fig. 6. — Near Views of Three Typical Fractures 

of from 4.7 per cent, to 8.7 per cent, in ultimate strength per square 

inch. 

A study of the results of the 4 X 3 X f inch angles without lugs 
shows that there is a gain of 8 per cent, in the strength per square 
inch for specimens having the line of pull coinciding with the pro- 
jection of the centre of gravity line instead of the gauge line for 



Tension Tests of Steel Angles 



313 



rivets. It further appears that for these angles the strength per 
square inch is practically the same for those specimens having the 
centre of gravity connections without lugs as it is for those having 
the gauge line connections with lugs. 



TABLE III — Showing Value of Lugs 



Type. 




Ultimate strength 

per square inch of 

net Section. 


Increase in strength 

per square inch of 

net area. 

% 


Ai 


Without lug 


47,400 


. . 


A2 


With lug 


49,600 


4.7 


Bi 


Without iug 


40,100 


. . 


B2 


With iug 


43,600 


8.7 


Ci 


Without lug 


41,400 


. . 


C2 


With lug 


43,200 


4.4 


Di 


Without lug 


47,400 


. . 


D2 


With lug 


50,600 


6.8 



Notwithstanding the fact that the net as well as the gross area 
of the two 3 X 3 X y g inch angles is less than in any of the single 
6X4X1 inch specimens, yet the ultimate load carried by the former 
is greater in every case. 

This is, no doubt, largely due to the greater strength of the material 
in the double specimens on account of their smaller size and thickness. 

In closing, the writer wishes to express his obligations to Messrs. 
Arthur L. Davis and S. P. Waldron, of the American Bridge Company, 
for the specimens tested, and to Messrs. A. F. Holmes, instructor, and 
C. T. Bartlett and H. P. Orcutt, students in the Massachusetts Institute 
of Technology, who carefully did the work in the laboratory. 



